Strong Moire Excitons in High-Angle Twisted Transition Metal Dichalcogenide Homobilayers with Robust Commensuration

The burgeoning field of twistronics, which concerns how changing the relative twist angles between two materials creates new optoelectronic properties, offers a novel platform for studying twist-angle dependent excitonic physics. Herein, by surveying a range of hexagonal phase transition metal dichalcogenides (TMD) twisted homobilayers, we find that 21.8 +/- 1.0 degrees-twisted (root 7a x root 7a) and 27.8 +/- 1.0 degrees-twisted (root 13a x root 13a) bilayers account for nearly 20% of the total population of twisted bilayers in solution-phase restacked bilayers and can be found also in chemical vapor deposition (CVD) samples. Examining the optical properties associated with these twisted angles, we found that 21.8 +/- 1.0 degrees twisted MoS2 bilayers exhibit an intense moire exciton peak in the photoluminescence (PL) spectra, originating from the refolded Brillouin zones. Our work suggests that commensurately twisted TMD homobilayers with short commensurate wavelengths can have interesting optoelectronic properties that are different from the small twist angle counterparts.